In the blue corner, the defender, the world wide web superstar, having no less than 70% of website using it as their server-side solution, the good friend of all daddy's personnal homepages, the companion of some of the top-ten biggest websites in the world including Wikipedia and Wordpress.com, having a tons of fans and a tons of haters, here is the three-letters world wide famous P... H... P... !

In the red corner, the challenger, the rising star of web's server-side solution, the solution of choice for any real-time, modern & reactive applications, using the programming language the most used in the world, the interpreted language powered by the fastest engine in the world, a language with an ever-growing popularity and use cases that even gnome-shell used it to create apps, a language with "good parts"... and bad parts, the most misunderstood language, here is Node.js & Javascript!

Some backgrounds of mine

Since 2007, I was a big fan of PHP.

PHP has a friendly learning curve and open up a whole world of possibility.

At that time, it was crystal clear to me that I MUST master this technology. I'm not into Windows, so ASP, .NET & co was not fitting my usual dev environment and philosophy. I have always found that Java's technologies was bloated and cumbersome. Perl looks too esoteric for me, Python looked interesting, but PHP's ecosystem was already beating those two for web applications.

So, at that time, learning PHP was the good choice for me.

Later, I was hired to build a large application, a full-featured project management SaaS, with file-sharing and file-synchronization.

Then a new player appears: Node.js.

I first heard it when I was searching for a decent way of using websocket alongside with PHP. That was really a pain in the neck. However, the young Node.js was already the best solution for that task.

Later, I was searching for an alternative for my company's file-sharing/file-synchronization service.

PHP was not exactly the better tools for that.

I put a lot of love and engineering into my PHP algorithm, so it worked pretty well for years, but as people join and add thousands of files, it becomes more and more complicated to scale.

Meanwhile, internet has changed...

People were more and more used to real-time application. The old request-response server paradigm was begining to fall apart. Our file-synchronisation service used to receive a request for update every 2 minutes per client applications.

But then our customers wanted real-time.

They wanted that when a coworker add a new file, the file would appears immediately on all the company's computers.

Reducing the update delay was not an option: it would cost at least +25% of resources to support one request per minute per client, and still, the customers would argue that one minute is not real-time. Perhaps one request every 10 seconds would pleased them, but this service would cost us at least four times more resources, not to mention the scalability nightmare.

If our customers want real-time, we need a persistent connection: the client should be wired to the service, and Websocket is the solution. So again, I considered Node.js for that task.

I started to realize that the web was changing, and that the good old PHP doesn't fit the new deal very well.

So I started learning intensively Node.js in the middle of 2013.

And believe me or not: it's a true love story.

The Node.js paradigm was blowing my mind, this wonderful event-driven/asynchronous/non-blocking I/O thing can do wonders. This model is just what make NginX kick Apache's ass. Its natural affinity with real-time and cutting edge technologies was really appealing.

Finally, we can code both side with the same language (No! Do not insist! Java is NOT an option! Come on: nobody is using browser-side Java anymore, the Dark Age is over).

Also Node.js is capable of more than just webservices, it can be used as a general purpose language/runtime, for various applications, even desktop applications and games using node-webkit / nw.js or atom-shell / electron.

Also, I found out that Node.js has a really fine community.

Here people are enthusiast, people are curious, people are happy. People are humble here, something really rare nowadays, since the Java's spirit has spread the world with its arrogant and obscurantist mindset, and now the majority of coders are passionless, serious and pretentious people. As for PHP, I always found it has a bloated community.

So thanks to Node.js, I have finally decided to go out of the dark, and start publishing various tools of mine. Thanks to the wonderful NPM registry, it is really easy and friendly.

Keyboard inputs!

Raw mode is the other of the two character-at-a-time modes. The line discipline performs no line editing, and the control sequences for both line editing functions and the various special characters ("interrupt", "quit", and flow control) are treated as normal character input. Applications programs reading from the terminal receive characters immediately, and receive the entire character stream unaltered, just as it came from the terminal device itself.

The first thing you need to know: your program will not exit when you hit CTRL-C anymore. Instead, you will have to watch for CTRL-C and use process.exit() by yourself.

isCharacter boolean is true if this is a regular character, i.e. not a control character

codepoint number (optional) the utf-8 code point of the character, if relevant

code number or Buffer, for multibyte character it is the raw Buffer input, for single byte character it is a number
between 0 and 255

Usually, if the name argument's length is 1, this is a regular character, if it is longer, it is a special key code, like CTRL_C, ENTER, DELETE, TAB, UP , HOME , F1, and so on... But be careful! A single asian character (Chinese, Japanese and Korean) always has a length of 2, so you should not rely on that and instead always data.isCharacter if you want to know if it is a true regular character or not.

Note that there are few issues with the way keys produce inputs in a terminal application that you should be aware of.

That's not the lib that should be blamed for that, but the way terminals actually works. Have in mind that it's not a kind of keyboard driver that pass keys to our application, we are just reading from the Standard Input stream (STDIN). And that's your terminal that pushes bytes into that STDIN stream.

For that purpose, the matches argument contains all matched keys. This is because sometimes, the input stream produces code that matches many possibilities. E.g. ENTER, KP_ENTER and CTRL_M are all producing a 0x0d in STDIN. TAB and CTRL_I both produce 0x09, BACKSPACE usually produces a 0x08 like CTRL_H, ...

When multiple matches happens, Terminal-kit will pass as the name argument the most useful matches. By the way ENTER has a greater priority than CTRL_M, TAB has greater priority than CTRL_I and BACKSPACE greater priority than CTRL_H.

Actually, all Ctrl-letter combo key produce a control character, i.e. one of the 32 lower ASCII character. But most of those control characters are useless nowaday, so it is safe to use almost all Ctrl-letter except CTRL_M, CTRL_I and CTRL_H.

Finally, you should be aware that special keys produce input in STDIN that vary greatly from one terminal to another. E.g. there is rarely two terminals that produce the same escape sequence for all F1 to F12 keys. Terminal-kit try to abstract that away from you, but exotic terminals can still causes some detection troubles. That's because there isn't any standard for that.

Also, some terminals like Gnome-terminal will intercept function keys for their own stuffs, e.g. F1 will open the Gnome-terminal help window, F11 will go fullscreen, ALT_F4 will close the window, and your application will never get those intercepted keys. So, the best practice is to bind multiple keys for the same action in your application. If you are going to use function keys, try to bind a function key and it's shift or ctrl variant to the same action, e.g. F1, CTRL_F1 and SHIFT_F1: if the terminal intercepts F1, there are chances that SHIFT_F1 will work...

Even better, if it's relevant and you can afford it, allow your users to configure their own key binding.

When you are done with user input, you can turn input grabbing off with .grabInput( false ). The terminal will leave the raw mode and returns to the cooked mode.

MOUSE_BUTTON_RELEASED: a button were released, however the terminal does not tell us which one.

MOUSE_MOTION: if the option { mouse: 'motion' } is passed to grabInput(), every moves of the mouse will fire this event, if { mouse: 'drag' } is given, it will be fired if the mouse move while a button is pressed.

Again, there are some issues to be aware of.

Firstly, do not expect all terminals to emit all *_RELEASED subtype. You should not rely on this, or you should at least have some fallbacks. E.g. Gnome-terminal emits MOUSE_LEFT_BUTTON_RELEASED and MOUSE_RIGHT_BUTTON_RELEASED, but does not emit MOUSE_MIDDEL_BUTTON_RELEASED... don't ask me why... -_-'

Secondly, do not expect all terminals to support the option { mouse: 'motion' }. E.g. the KDE Konsole will only report the MOUSE_MOTION event-subtype when a button is pressed, the same way it works with the { mouse: 'drag' } mode.

Thirdly, some terminals intercept right click to display a context menu. Gnome-terminal used to do that, but it seems that newer versions (at least on my Fedora at time of writing) don't do that anymore when the terminal has switched to raw mode, which was done with .grabInput().

By the way, the good old Xterm works perfectly fine! Outdated UI/UX, but extremely reliable when it comes to raw features support.

The Ultimate Geek Touch: Terminal-kit even supports the mouse in the Linux Console by talking directly with the GPM driver if it is installed on your box. Seriously, I'm quite proud of that, since I have almost done reverse engineering to provide that. Yay, there is no documentation for the GPM driver, so one have to: read the source code, watch inputs and outputs, guess how it works, repeat.

Putting it all together

Here a small sample code that allows one to write anywhere on the screen, using arrow keys to move while other keys are echoed:

Misc inputs with the 'terminal' event

The terminal event is a general purpose event for all things coming from your terminal that are not key or mouse event.

The terminal event is emitted with two arguments:

name string the name of the subtype of event

data Object provide some data depending on the event's subtype

The SCREEN_RESIZE subtype is emited when the terminal is resized by the user. The data argument will contain the width and height property: the new size of the screen expressed in characters.

Finally, if .grabInput() was called with the { focus: true } option, a terminal event will be emited with FOCUS_IN or FOCUS_OUT subtype when the terminal gains or loses focus. Not all terminal supports that.

Next time?

So, we have learn many interesting things, but we have not explored all features Terminal-kit has.

Next time we will learn how to use higher level user-inputs methods, like .inputField().

This tutorial will focus exclusively on the terminal-kit lib for Node.js. Make sure to npm install terminal-kit before trying the given examples.

For those who have already done some C/C++ coding with Ncurses, you may know that there is a saying:

More than often, a programmer dealing with Ncurses will curse.

The goal of terminal-kit is to provide a simple and modern way to interact with the terminal. The design should be simple and intuitive, and yet give maximum power in the hand of the user. Hopefully, you will say goodbye to the good ol' Ncurses' days!

Moving the cursor

That cannot be easier!

To move the cursor relative to its position:

.up( n ): move the cursor up by n cells

.down( n ): move it down by n cells…

.left( n ): …

.right( n ): …

.nextLine(n): move the cursor to beginning of the line, n lines down

.previousLine(n): move the cursor to beginning of the line, n lines up

This creates a status bar with a white background and black text color, on the top of the screen. The update code saves the cursor's position and restores it, so it doesn't disturb the main text flow, that's why it still writes Mike says: "Hey hey hey!" as if no cursor movement happened.

Editing the screen

Now that we've learn how to move the cursor, let's see how to edit what is already displayed.

Let's see what we can do:

.clear(): clear the screen and move the cursor to the upper-left corner

.eraseDisplayBelow(): erase everything below the cursor

.eraseDisplayAbove(): erase everything above the cursor

.eraseDisplay(): erase everything

.eraseLineAfter(): erase current line after the cursor

.eraseLineBefore(): erase current line before the cursor

.eraseLine(): erase current line

.insertLine(n): insert n lines

.deleteLine(n): delete n lines

.insert(n): insert n char after (works like INSERT on the keyboard)

.delete(n): delete n char after (works like DELETE on the keyboard)

.backDelete(): delete one char backward (works like BACKSPACE on the keyboard), shorthand composed by a .left(1) followed by a .delete(1)

E.g., move the cursor and then erase anything below it to clean the area:

term.moveTo( 1 , 5 ) ;
term.eraseDisplayBelow() ;

For all erase-like methods, note that the screen is erased using the current background color! Hence, if we wanted to erase the screen, and paint anything below the cursor with a red background, we can modify the above code this way:

term.moveTo( 1 , 5 ) ;
term.bgRed() ;
term.eraseDisplayBelow() ;

This apply to .clear() as well, so term.bgBlue.clear() will erase the whole screen, paint it blue, and move the cursor to the top-left corner.

Also there is the advanced method .fullscreen( true ) (not chainable) that clears the screen, moves the cursor to the top-left corner, and if the terminal supports it, it turns the alternate screen buffer on.

If alternate screen buffer is available, when you invoke .fullscreen( false ), the screen will be restored into the state it was before calling .fullscreen( true ).

This is really a key feature for writing cool terminal application! Now you can code something that behaves like the htop linux command, using the whole terminal display area, and when users quit your app, the command history of their shell will be restored. Neat!

If alternate screen buffer is not supported by your terminal, it will fail gracefully.

Last words

Now the cool factor: you can change your terminal window's title with the method .windowTitle():

term.windowTitle( "My wonderful app" )` ; // set the title of the window to "My wonderful app"

Hehe ;)

Next time we will focus on input: keyboard and mouse!

I hope you have found this tutorial useful, and will be happy if you drop me a line or two!

Prologue

Have you ever wanted to make your CLI script shine? While cool scripts expose colors and styles, you are still stuck with black & white boring text? Hey! I've got something for you!

In this series of article, we will explore how to build a great terminal application: how to move the cursor, edit the screen, handle keyboard input, handle mouse input, and even more goodies!

But let's start with something simpler... Life is really bland without colors, doesn't it?... Let's add some spicy colors to our terminal application!

The hard way

You wonder how colors and styles are achieved? You guess that one have do deal with an obscur underlying driver? Actually, you're wrong: you can do that with a simpleconsole.log().

So let's write a red "Hello world!":

console.log( '\x1b[31mHello world!' ) ;

Yes, you guessed it: \x1b[31m is an escape sequencethat will be intercepted by your terminal and instructs it to switch to the red color. In fact, \x1b is the code for the non-printable control character escape... you know, that key on the top-left corner of your keyboard?

Eventually, if we want to produce a notice of this kind: Warning:the error #105 just happened!
... you will have to code this:

The outsider: terminal-kit

The basic part of terminal-kit, the part dealing with styles and colors was inspired by chalk. It's easy, you can combine styles and colors, and furthermore, you don't have to use console.log() anymore. Why? Because terminal-kitIS a terminal lib, not just an ANSI's style helper.

Just compare the chalk's way:

console.log( chalk.blue.bold( 'Hello world!' ) ) ;

... and the terminal-kit's way:

term.blue.bold( 'Hello world!' ) ;

Less cumbersome, right?

This is the spaceship demo! After doing an npm install terminal-kit, go to node_modules/terminal-kit/demo/ and run ./spaceship.js to see it alive!

Okey, what if you don't want to output a string directly on the terminal, but just put it into a variable like colors and chalk does? Easy: just add the str property into your chainable combo:

var myString = term.red.str( 'Hello world!\n' ) ;

It happens that at least 95% of time, we deal with color only when we are about to output something directly into the terminal, and don't care about storing a string containing obscur escape sequences into some variable... That's why the default behaviour of the lib is to print, not to return.

If you want to output to stderr instead, just add the error property into your chainable combo:

It's worth noting that providing some text to a style method will apply the color *ONLY* for the given text, while calling a style method without text will turn the current style on, until another style contradict that.

Truthy and Falsy

First, we need to understand the truthy and falsy concept, because it will be widely used in the second part.

Truthy and falsy is a common concept among dynamic language featuring loose typing.

Any value, whatever the type, belong to the truthy or falsy group. When an operator need a boolean value, truthy will be true and falsy will be false.

Those values are falsy:

undefined
null
false
0
NaN
''

Those values are truthy:

true
1
123 // any numbers that are not 0 are truthy
'some random string' // any non-empty string are truthy
[] // any array are truthy, even empty arrays
{} // any object are truthy, even empty objects, except null (yay, null is an object...)

An if statement will execute its block of code if the expression is truthy.

if ( expression )
{
// if expression is truthy, the following lines are executed
...
}
else
{
// if expression is falsy, the following lines are executed
...
}

Syntactic Sugar

Here an unordered list of shortcuts that eases life and helps maintaining a neat and elegant codebase.

!! expression: a very elegant way to cast a variable or an expression into a boolean, much more pleasant than the cumbersome expression ? true : false. It is also known as the double not. How it works? ! returns the inverse boolean value of an expression. Apply it twice and you are back to the original logical value of the expression, casted as a boolean.

+ stringExpression: it converts a string expression into a number, e.g. typeof + '42' === 'number' is true. It works if + is used as an unary operator, when there are no left member.

+ new Date(): it converts the Date value into a number, same mechanics than the previous one.

optionalArgument || defaultValue: it returns optionalArgument if it is truthy, else it returns defaultValue. || is sometime refered as the default operator. In Javascript, the || and && operator are a bit like flow controle, they don't produce booleans, but instead they return the last evaluated operand. Still, the returned operand is considerated truthy or falsy according to the logical rules of AND and OR operators.

Also, the first variable was named optionalArgument on purpose. Because it is an elegant way to define default parameter for functions when the type of the parameter is expected to be always truthy (object, array). Do not use when falsy values are expected.

object && object.child && object.child.property: this is the guard operator, allowing us to safely access the property of nested objects. Without that, accessing directly object.child.property would raise an error if object was not an object, or if object has no child property.

!a !== !b: this is the easiest way to achieve a logical XOR (eXclusive OR) in Javascript. This expression is true if a is truthy or b is truthy, but not both of them. The not operator cast a and b to boolean (while reversing their logical value), then if they are different, one and only one of them is true, therefore the whole expression is true.

Feel free to comment and share your own favorite syntactic sugar with us!